A quantitative evaluation of aerosol generation during tracheal intubation and extubation

Abstract

Summary The potential aerosolised transmission of severe acute respiratory syndrome coronavirus‐2 is of global concern. Airborne precaution personal protective equipment and preventative measures are universally mandated for medical procedures deemed to be aerosol generating. The implementation of these measures is having a huge impact on healthcare provision. There is currently a lack of quantitative evidence on the number and size of airborne particles produced during aerosol‐generating procedures to inform risk assessments. To address this evidence gap, we conducted real‐time, high‐resolution environmental monitoring in ultraclean ventilation operating theatres during tracheal intubation and extubation sequences. Continuous sampling with an optical particle sizer allowed characterisation of aerosol generation within the zone between the patient and anaesthetist. Aerosol monitoring showed a very low background particle count (0.4 particles.l −1 ) allowing resolution of transient increases in airborne particles associated with airway management. As a positive reference control, we quantitated the aerosol produced in the same setting by a volitional cough (average concentration, 732 (418) particles.l −1 , n = 38). Tracheal intubation including facemask ventilation produced very low quantities of aerosolised particles (average concentration, 1.4 (1.4) particles.l −1 , n = 14, p < 0.0001 vs. cough). Tracheal extubation, particularly when the patient coughed, produced a detectable aerosol (21 (18) l −1 , n = 10) which was 15‐fold greater than intubation (p = 0.0004) but 35‐fold less than a volitional cough (p < 0.0001). The study does not support the designation of elective tracheal intubation as an aerosol‐generating procedure. Extubation generates more detectable aerosol than intubation but falls below the current criterion for designation as a high‐risk aerosol‐generating procedure. These novel findings from real‐time aerosol detection in a routine healthcare setting provide a quantitative methodology for risk assessment that can be extended to other airway management techniques and clinical settings. They also indicate the need for reappraisal of what constitutes an aerosol‐generating procedure and the associated precautions for routine anaesthetic airway management.

Are tracheal intubation and extubation aerosol‐generating procedures?

“…Dhillon et al [6] report their findings in cm -3 and, for the purpose of this editorial, we have converted their data to l -1 to allow direct comparison with Brown et al [7]. Both groups 3 The difference in sampling locations between these two studies: we still have a poor understanding of the temporal and spatial dispersion of aerosols from tracheal intubation and aerosol measurement results are likely to be time-and location-dependent based on these two studies.…”

“…Whether or not these pose a clinically significant risk depends on the number, size and concentration of infectious aerosols [5]. In this issue of Anaesthesia, there are two papers using robust scientific approaches to evaluate aerosol generation during tracheal intubation and extubation to address this gap in evidence [6,7]. From these two studies, it can be confirmed that tracheal intubation and extubation does produce a certain number of aerosols which can remain suspended and spread in the operation room air; but does this research provide any reassurance as to whether what we are currently doing is safe or appropriate?…”

Aerosol containment device for airway management of patients with COVID-19: a narrative review

“…An observational study has confirmed that the risk of the spread of viral droplets and aerosols is minimum during induction of anesthesia and during tracheal intubation [32]. This study, in which aerosol concentrations near the patient's mouth were measured, has shown that aerosol level was minimum during induction of anesthesia and tracheal intubation, which was 500-fold less than the average concentration recorded during coughing.…”

“…This study, in which aerosol concentrations near the patient's mouth were measured, has shown that aerosol level was minimum during induction of anesthesia and tracheal intubation, which was 500-fold less than the average concentration recorded during coughing. In contrast, aerosol concentration was increased markedly during emergence from anesthesia, and the concentration was 15-fold greater than that seen during tracheal intubation [32]. From these results, it is reasonable to conclude that an aerosol containment device has a much less use during induction of anesthesia than during emergence from anesthesia.…”

Controversies in airway management of COVID-19 patients: updated information and international expert consensus recommendations

“…Recommendations for the personal protective equipment (PPE) required during aerosol-generating procedures (AGPs), such as advanced airway management, are inconsistent amongst different countries and regions. 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 Two new studies report conflicting results, either supporting 9 or opposing 10 tracheal intubation and extubation as AGPs. Both studies were limited by small sample size, and used different definitions of AGPs and particle detection methods.…”